Pinch detection system

Abstract

A pinch detection system and method controls the speed of a motor moving an object by first calculating the actual motor force and then comparing the actual motor force with a reference force value in a reference field. A pinch condition is indicated if the difference between the actual force and the reference force exceeds a selected pinch threshold. The difference is also used to update the reference field, the pinch threshold and the desired speed of the motor so that the reference field will eventually reflect the actual force profile of the object. The updated pinch threshold is also used to control the motor speed so that the pinching force remains constant regardless of the pinch threshold value.

1. A system that detects a pinch condition for a moving object, comprising:
 a motor that controls movement of the object;  
 a pinch detector that determines a difference between an actual force and a reference force, wherein the pinch detector indicates a pinch condition if the difference exceeds a pinch detection threshold; and  
 a motor regulator that changes operation of the motor if the pinch detector indicates a pinch condition,  
 wherein at least one of the pinch detection threshold, the reference force, and a desired motor speed is updated based on the difference between the actual force and the reference force.  
 wherein the actual force is a value in a force profile having a plurality of actual force values and the reference force is a value in a reference field having a plurality of reference force values.  
 
   
   
     2. The system af  claim 1 , wherein the object is at least one selected from the group consisting of a vehicle door, a vehicle window, a sliding door, a trunk, and a lift gate. 
   
   
     3. The system of  claim 1 , wherein the pinch detector indicates the pinch condition by setting a pinch detection flag, and wherein the motor regulator reverses the motor if the pinch detection flag is set. 
   
   
     4. The system of  claim 1 , wherein the pinch detector calculates the pinch threshold based on a maximum difference between the actual force values in the force profile and the reference force values in the reference field. 
   
   
     5. The system of  claim 4 , wherein the pinch threshold is updated by calculating an additional threshold value from the maximum difference. 
   
   
     6. The system of  claim 5 , wherein the additional threshold value is set equal to the maximum difference when a change in the maximum difference is less than a selected change value, and wherein the additional threshold value is set equal to the maximum difference plus the selected change value if the change in the maximum difference is greater than the selected change value. 
   
   
     7. The system of  claim 5 , wherein the desired speed is updated by adding a nominal desired speed to the additional threshold value multiplied by a proportional factor. 
   
   
     8. The system of  claim 7 , wherein the proportional factor is varied to reduce the desired speed as the additional threshold value increases to keep a pinching force of the system constant. 
   
   
     9. The system of  claim 1 , wherein the reference force is updated by adding together the reference force and a value proportional to the difference between the actual force and the reference force. 
   
   
     10. The system of  claim 1 , further comprising:
 a speed sensor that detects a motor speed;  
 a voltage sensor that measures a voltage across the motor; and  
 a force calculator coupled to the voltage sensor and the speed sensor, wherein the force calculator calculates the actual force from the voltage across the motor and the motor speed.  
 
   
   
     11. The system of  claim 1 , further comprising at least one memory location that stores initial values of the pinch detection threshold, the reference force, and the desired motor speed. 
   
   
     12. A system that detects a pinch condition for a moving object, comprising:
 a motor that controls movement of the object;  
 a speed sensor that detects a motor speed;  
 a voltage sensor that measures a voltage across the motor;  
 a force calculator that determines the actual force from the voltage across the motor and the motor speed, wherein the actual force is a value in a force profile having a plurality of actual force values corresponding to a plurality of object positions;  
 a reference field having a plurality of reference force values corresponding to the plurality of object positions;  
 a pinch detector that determines a difference between an actual force calculated from the motor speed with a reference force from the reference field, wherein the pinch detector sets a pinch detection flag if the difference exceeds a pinch detection threshold; and  
 a motor regulator that reverses the motor if the pinch detection flag is set,  
 wherein at least one of the pinch detection threshold, the reference field, and a desired motor speed is updated based on the difference between the actual force and the reference force,  
 wherein the pinch threshold is updated by calculating an additional threshold value from a maximum difference between the actual force values in the force profile and the reference force values in the reference field, the desired speed is updated by adding a nominal desired speed to the additional threshold value multiplied by a proportional factor, and the reference field is updated by adding together the reference force and a value proportional to the difference between the actual force and the reference force.  
 
   
   
     13. The system of  claim 12 , wherein the object is at least one selected from the group consisting of a vehicle door, a vehicle window, a sliding door, a trunk, and a lift gate. 
   
   
     14. The system of  claim 12 , wherein the additional threshold value is set equal to the maximum difference when a change in the maximum difference is less than a selected change value, and wherein the additional threshold value is set equal to the maximum difference plus the selected change value if the change in the maximum difference is greater than the selected change value. 
   
   
     15. The system of  claim 12 , wherein the proportional factor is varied to reduce the desired speed as the additional threshold value increases to keep a pinching force of the system constant. 
   
   
     16. The system of  claim 12 , further comprising at least one memory location that stores initial values of the pinch detection threshold, the reference field, and the desired motor speed. 
   
   
     17. A method for detecting a pinch condition for an object moved by a motor, comprising:
 calculating a difference between an actual force applied by the motor and a reference force;  
 setting a pinch detection flag if the difference exceeds a pinch detection threshold;  
 changing operation of the motor if the pinch detection flag is set; and  
 updating at least one of the pinch detection threshold, the reference force, and a desired motor speed based on the difference between the actual force and the reference force, wherein the actual force is a value in a force profile having a plurality of actual force values and the reference force is a value in a reference field having a plurality of reference force values, and wherein the pinch threshold is updated based on a maximum difference between the actual force values in the force profile and the reference force values in the reference field.  
 
   
   
     18. The method of  claim 17 , wherein calculating the actual force comprises:
 measuring a speed of the motor;  
 measuring the voltage across the motor; and  
 calculating the actual force from the measured speed and voltage.  
 
   
   
     19. The method of  claim 17 , wherein the act of updating includes calculating an additional threshold value from the maximum difference. 
   
   
     20. The method of  claim 19 , wherein the updating act sets the additional threshold value equal to the maximum difference when a change in the maximum difference is less than a selected change value, and wherein the updating act sets the additional threshold value equal to the maximum difference plus the selected change value if the change in the maximum difference is greater than the selected change value. 
   
   
     21. The method of  claim 19 , wherein the act of updating the desired speed includes adding a nominal desired speed and the additional threshold value multiplied by a proportional factor. 
   
   
     22. The method of  claim 21 , further comprising varying the proportional factor to reduce the desired speed as the additional threshold value increases to keep a pinching force of the system constant. 
   
   
     23. The method of  claim 17 , wherein the act of updating the reference force includes adding together the reference force and a value proportional to the difference between the actual force and the reference force.